Drug Interaction Report

MONITOR: Coadministration with bosentan may decrease the plasma concentrations of drugs that are substrates of the CYP450 2C9 and/or 3A4 isoenzymes. The mechanism is accelerated clearance due to induction of those isoenzymes by bosentan.

MANAGEMENT: When drugs that are known substrates of CYP450 2C9 and/or 3A4 are coadministered with bosentan, the possibility of a diminished therapeutic response to those drugs should be considered. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs, particularly those with a narrow therapeutic range, whenever bosentan is added to or withdrawn from therapy.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.